The use of artificial teeth and dentures to replace natural teeth has been known for centuries. In modern times, artificial teeth are made chiefly from polymethyl methacrylate and to a lesser extent from the glass-ceramics and from dental porcelains. To prepare a complete artificial denture for a patient, the dentist first takes impressions of the patient's residual dental arches, from which the natural teeth have been lost. An impression material like polysiloxane can be used. An impression is taken of the patient's upper jaw and a lower impression of the lower jaw. Artificial dental stone casts or models are poured from these impressions. On these casts, wax rims are prepared and these rims are carved by the dentist until the correct facial and lip contours are supported by them. The rims are finally fixed together in occlusion i.e. in contact, to register the relationship of the lower jaw to the upper jaw, commonly known as "the bite". Artificial teeth are set-up into the wax occlusion rims to trial denture stage by the dentist, or more usually by a dental technician. Wax-based trial dentures, with the artificial teeth affixed, are then assessed for appearance and fit in the patient's mouth. When an acceptable appearance, good fit and correct bite are achieved, the wax of the trial dentures is replaced with acrylic. This is done by making a gypsum mould for each denture, upper and lower, and by boiling out the wax. It is replaced with a material like polymethyl methacrylate. The teeth on the plastics dentures are in the same position as they were in the wax trial dentures.
Conventionally, artificial teeth are supplied by a manufacturer arranged on four separate tooth-cards. Typically, there are the six upper anterior teeth, the six lower anterior teeth, the eight upper posterior teeth (four on either side) and the eight lower posterior teeth (four on either side). The teeth are matched by mould and by shade and the manufacturer can dispense the four cards as a display unit. A dentist may use the teeth as a set, for a complete artificial dentition, but the customary method of arranging the teeth of artificial dentures is to remove individual teeth from the cards and place them on the wax bases until they simulate the natural teeth of a patient. Eventually, fourteen upper teeth are set-up on a wax base and fourteen lower teeth on a lower wax rim are prepared as a complete trial denture of up to twenty-eight teeth. The positions of the teeth can be further adapted by the dentist to the exact requirements of a patient before the dentures are completed.
DE-A-39 10 393 relates to an external jig having an arch-shaped hollow frame (1) in which is formed a plurality of shaped apertures (8) to receive the occlusal surfaces (i.e. cut ring surfaces) of artificial teeth. Thus, the "backs" or bases of the teeth extend outwardly of the jig so that they can be pressed by the jig into the underlying wax baseplate (5).
The known arrangements have the disadvantage that they are very time consuming. Because each tooth must be set individually on a wax trial base or on a jig, it can take a dental technician several hours to set the teeth correctly. Also, considerable skill is required in selecting the particular teeth to achieve dentures having a desired cosmetic effect and with a harmonious occlusion between upper and lower sets of teeth.